A high school senior was shot to death outside a fast-food restaurant after fistfights broke out among youths who had gathered there after school, authorities said. An 18-year-old man was arrested Friday.

Some witnesses suggested the shooting Thursday was gang-related, but authorities characterized it more as a territorial dispute.

The shots were fired by a man who had gotten out of a white van after several fistfights between groups of youths across from King High School in a crowded McDonald's parking lot. The shooter then sped off, deputies said.

Witnesses said the slain youth, 17-year-old Dalshon Walton, was shot as he started to walk away from the crowd. Investigators were trying to determine if he had been involved in the dispute or just got in the way.

"All this shouldn't have gone down. It was petty. It was stupid," friend Alejo Vickers, 19, told the St. Petersburg Times.

Walton died at a hospital, the sheriff's office said. Three people wounded, ages 15, 16 and 19, were treated at hospitals and released.

Otis Lorenzo Neal was arrested Friday at an acquaintance's apartment, authorities said. He was charged with second-degree murder and three counts of aggravated battery with a firearm, the sheriff's office said.

Neal was in jail in lieu of $22,500 bond. It was unclear whether he had a lawyer.